The Martin patent U.S. Pat. No. 3,745,977 and my patent U.S. Pat. No. 4,559,905 utilize the buoyancy of the water to close an access opening into the water reservoir by the upward buoyant force being applied to the closure element seated in the access opening. Should the water freeze, the closure element would become inoperative as it would be immovable in the ice.
While the buoyant closure element is insulated, it will still transmit some heat from the water reservoir to the atmosphere outside the animal waterer due to its contact with the water in the reservoir.
Ritchie Industries, Inc. Conrad, Iowa sells an animal waterer having a ballast positioned in the water in the water reservoir connected to a cable which extends over a pulley mounted in the top section of the waterer which in turn extends downwardly into engagement with a closure element. This waterer suffers from numerous problems. The ballast in the water is subject to freezing and becoming inoperative. Should debris collect in the water reservoir the ballast will not be free to move and consistently maintain the valve or the closure element in a closed position. The pulley being mounted in the top unit makes it awkward assembling and disassembling the animal waterer when the top is removed and assembled. The cable will also be subject to corrosion due to being in the water.